The present invention relates to a rubber composition for a tread.
Among parts of a tire, a tread is a part particularly affecting to rolling resistance of a tire, and in order to lower the rolling resistance, compounding silica as a filler for reinforcement is generally carried out.
Since a rubber composition for a tread is easily aged with heat and the like generated by running, it is required to have excellent heat aging resistance.
In the step of vulcanizing the rubber composition for a tread comprising silica, as a vulcanization speed increases to be high, there arise problems such as causing early vulcanization (scorch) due to the influence of a silane coupling agent used in combination with silica and so it is necessary to carry out the vulcanization at an suitable vulcanization speed.
Thus, the rubber composition for a tread comprising silica is required to be excellent in the heat aging resistance and prepared at a suitable vulcanization speed, and in order to satisfy these requirements, particular vulcanization accelerators have been conventionally compounded.
JP-A-2002-226629 discloses a rubber composition for a tread comprising tetrabenzylthiuram disulfide and N-cyclohexyl-2-benzothiazolylsulfenamide as a vulcanization accelerator, but it did not positively compounded with silica, and when silica is used, there has been a problem that silica adsorbs the vulcanization accelerator and, thus, vulcanization is delayed.